Home health care practitioners routinely draw blood for analysis from homebound patients. Once drawn, whole blood begins to hemolyze resulting in chemical changes that affect testing accuracy. Inaccurate test results can cause the wrong treatment to be prescribed for the donor. Additionally, should the sample be identified as hemolyzed, another sample must be taken from the patient, increasing the risk of complications related to venipuncture such as infection, cellulitis, excessive bleeding, and blood clots. Further, multiple venipunctures could be necessary to acquire the necessary sample. Regardless of complications, each extra venipuncture subjects the donor to unnecessary pain.
To combat hemolysis, whole blood must be delivered to a laboratory for analysis within thirty minutes of being drawn. Accordingly, a home health care practitioner is typically required to go to a lab after each patient visit, even where multiple patients live within close proximity. This reduces the efficiency of the home health care practitioner and generates additional medical expenses in the form of additional time and mileage.
Another solution is to separate whole blood into its constituent components immediately, thereby stopping the hemolyzation process. However, this would require that a centrifuge be present after blood is drawn from the body. Conventional centrifuges are heavy, unwieldy devices unsuitable for use in the field.
Several devices have been produced to separate fluids using centrifugal forces. Typical of the art are those devices disclosed in the following U.S. Pat. Nos.:
______________________________________ U.S. Pat. No. Inventor(s) Issue Date ______________________________________ 3,954,611 Reedy May 4, 1976 4,412,831 Avery et al. Nov. 1, 1983 4,530,691 Brown Jul. 23, 1985 4,636,193 Cullis Jan. 13, 1987 4,889,524 Fell et al. Dec. 26, 1989 4,924,770 Raub May 15, 1990 5,067,938 Uchida et al. Nov. 26, 1991 5,387,174 Rochat Feb. 7, 1995 5,505,683 Geringer et al. Apr. 9, 1996 ______________________________________
It is desirable to have a portable centrifuge for use at remote locations. Several U.S. Letter patents disclose mobile centrifuges which, while being transportable, are not easily carried to locations frequented by a home health care practitioner. For example U.S. Pat. No. 3,954,611 discloses a mobile centrifuge device for separating clean oil from dirty oil. The '611 device requires mounting upon a truck or a trailer to achieve mobility. Similarly, U.S. Pat. No. 4,924,770 discloses a mobile juice extraction machine having a centrifuge for separating juice from pulp. The '770 device includes a cabinet-mounted juice extractor supported on casters for moving the cabinet to different locations within a grocery store. Although these devices are "mobile" in the sense that they may be rolled from one room to another within a structure, they are certainly not practical for use in the home health care industry as they are not easily transportable from one location to another, nor are they hand-held.
Additionally, the type of centrifuge needed depends upon the reason for drawing blood. For example, plasma donation involves separating red blood cells from the plasma. This process is also used in surgical procedures wherein blood lost by the patient is collected and separated, the red blood cells being reintroduced into the patient's vascular system to aid in the recovery process. Plasmapheresis typically employs a drum centrifuge comprising a separation bowl having exit holes near the top and spinning at high speeds. As the bowl spins, the lighter fluid is forced upward within the bowl and eventually out of the outlet ports while the heavier fluid remains within the drum to be evacuated through a drain, often to be returned to the donor, as indicated in the above examples.
Conversely, during blood sample analysis, a small amount of blood is separated into constituent components using an eccentric centrifuge. An eccentric centrifuge employs a plurality of counterbalanced separation tubes secured within a member rotating at high speeds. The separation tubes are placed at an angle with respect to the rotating axis, with the bottom end farther from the axis than the top. Thus, during operation of the centrifuge, heavier components of the fluid sink to the bottom while lighter components rise to the top of the tube for easy extraction and/or measurement.
U.S. Pat. Nos. 4,412,831; 4,530,691; 4,636,193; 4,889,524; 5,067,938; 5,387,174; and 5,505,683 disclose various centrifuge devices, adaptations and improvements. Primarily, these patents teach centrifuges not suited for being hand carried. For example, the '831 patent and the '938 patent teach the use of centrifuges mounted on rollers.
The '524 patent discloses a portable centrifuge designed for plasmapheresis and monitoring the status of both the system and the patient. The '524 device includes a drum centrifuge, a blood pump, an audible alarm, three air detectors, a microprocessor, cooling fans, a pressure sensor, and a pressurizing pump contained within a cabinet. Additionally, the '524 device does not provide a leveling device for use upon uneven surfaces. Further, the '524 device is designed to centrifuge blood pumped directly from the donor's vein and not to accept a blood sample drawn by a syringe. Finally, the '524 device is not suited for centrifuging the low volume blood samples typically used for analysis.
Therefore, it is an object of this invention to provide an eccentric centrifuge which is compact and lightweight so as to be easily portable.
Another object of this invention is to provide a centrifuge having a device for static leveling of the centrifuge on any surface.
A further object of this invention is to provide a centrifuge capable of using a d.c. power source, such as that provided by a car cigarette lighter receptacle.